I don’t know how to do this

2x+9+2x+1+x+9+2x-9= 360
7x+10=360
7x=350
x=50
(now that you know the value of X, plug it in where you see X for angle A)
Angle A= 2x+1
2(50)+1=
100+1=
100
Angle A=100 degrees
X=50
Hello,
The sum of angles is 360°.
( 2x + 9) + ( 2x + 1) + ( x + 9 ) + ( 2x - 9 ) = 360°
2x + 9 + 2x + 1 + x + 9 + 2x - 9 = 360°
2x + 2x + 2x + x + 9 + 1 + 9 - 9 = 360°
7x + 10 = 360°
7x = 360 - 10 = 350
x = 350 / 7 = 50°
Bye :)